The present invention relates to an aqueous covering composition suitable for the applications to primer and paint to be used on painting polyolefinic resin moldings and containing no aromatic organic solvent at all.
Polyolefinic resins such as polypropylene have been used in large amounts for electrical appliances in house, parts of car, etc. because of excellent properties and low price. However, polyolefinic resins have a drawback of difficult painting and adherence due to nonpolarity. For this reason, it is common to use a primer having chlorinated polyolefin as a major ingredient at the time of painting and adhering polyolefinic resins. However, since chlorinated polyolefin only dissolves into aromatic organic solvents such as toluene and xylene, large amounts of aromatic organic solvent cannot help being used, which has been a problem from the aspects of safety and hygiene and environmental pollution.
Hence, attempts to produce aqueous dispersion of chlorinated polyolefin have been made and they are disclosed for example, in Japanese Unexamined Patent Publication No. Hei 1-153778, No. Hei 1-256556, Hei 2-284973, etc. In these, however, aromatic organic solvents are used on production and it was difficult to eliminate them completely. Also. attempts to produce aqueous dispersion of modified polyolefin have been made, which are disclosed, for example in Japanese Unexamined Patent Publication No. Sho 59-47244, No. Hei 2-286724, etc. They have, however, drawbacks such as poor adhesive property to polyolefin resin, poor water resistance and poor paintability and such aqueous compositions have not yet been put into practice.
As described, it is necessary to give the primer treatment to perform the painting and adhesion to polyolefinic resin, but the production of aqueous composition for paint containing no aromatic organic solvent at all and having good adhesive property to polyolefinic resin has been difficult technically. The purpose of the invention is provide an aqueous composition which solves such problematic points and can improve the paintability and adhesive property of polyolefinic resin.
As a result of extensive studies to achieve the purpose aforementioned, the inventors have reached the invention.